THE RELATIONSHIP OF BLADDER CANCER TO SMOKING

National Trends of Bladder Cancer and Trihalomethanes in Drinking Water: A Review and Multicountry Ecological Study

We examined trends in incidence of bladder cancer in 8 countries in the 45+ years since trihalomethanes (THMs) were detected in chlorinated drinking water. Total trihalomethanes (TTHMs) are the principal regulated disinfection by-products (DBPs) along with halogenated acetic acids (HAAs). Numerous epidemiological studies have examined exposure to TTHMs and associations with bladder cancer. Concentrations of TTHM have declined in most of the 8 countries that were studied as has smoking prevalence. Incidences of bladder cancer have usually stayed relatively flat, especially for females, with some variations. Since THMs are not carcinogens in whole animal tests, they may not be appropriate surrogates for studying potential cancer risks in drinking water. Etiology of bladder cancer is complex; incidence correlates with age. Previously identified risk factors include smoking, type 2 diabetes, sex, ethnicity, arsenic, aromatic amines, and occupations. As a predominant risk factor, smoking trends may dominate incidence rates, but additional time might be required to determine whether a DBP risk exists due to long latency periods. Causal drinking water-related bladder cancer risks remain questionable and likely small compared to other factors, although surrogate-based DBP management is an appropriate strategy for maintaining drinking water quality as long as it does not compromise microbial disinfection.

Inhalation of tobacco smoke induces increased proliferation of urinary bladder epithelium and endothelium in female C57BL/6 mice

Cigarette smoking is the major environmental risk factor for bladder cancer in humans. Aromatic amines, potent DNA-reactive bladder carcinogens present in cigarette smoke, contribute significantly. However, increased cell proliferation, caused by direct mitogenesis or in response to cytotoxicity, may also play a role since urothelial hyperplasia has been observed in human cigarette smokers. We examined the urothelial effects of cigarette smoke (whole body inhalation exposure (Teague) system) in female C57BL/6 mice at various times in two studies, including reversibility evaluations. In both studies, no urothelial hyperplasia was observed by light microscopy in any group. However, in study 1, the Ki-67 labeling index (LI) of the urothelium was significantly increased in the smoke exposed group compared to controls through 3 months, but was not present at 6, 9 or 12 months even with continued exposures. In the groups that discontinued smoke exposure, it returned to the same levels as controls or lower. In study 2, the bromodeoxyuridine LI was similar to controls on day 1 but significantly increased at 5 days in the smoke exposed group. In the group that discontinued smoke exposure for 2 days, the LI was increased compared to controls but not significantly. Superficial urothelial cell cytotoxicity and necrosis were detectable by scanning electron microscopy at 5 days. Changes in LI of submucosal endothelial cells generally followed those of the urothelium and effects were reversible upon cessation of exposure. The increased urothelial proliferation appeared to be due to superficial cell cytotoxicity with consequent regeneration.

Secondary malignant neoplasms in patients with bladder carcinoma

At the University of Pennsylvania and its affiliates, 292 patients with bladder carcinoma treated with a variety of definitive regimens were observed for the incidence of secondary malignancies. The cumulative incidence at fifty-four months, including synchronous primary neoplasms, was 24 percent. Hazard function analysis reveals a relatively constant risk of new neoplasms to be approximately 1.5 percent per year over a period of forty-eight months after diagnosis.

Variations of cortisol hydroxylation and paracetamol metabolism in patients with bladder carcinoma

We investigated the possibility that variations of the metabolism of xenobiotic compounds might be involved in the process of bladder carcinogenesis, by studying activation reactions (phase I) and detoxification reactions (phase II) of xenobiotic compounds in a group of patients with transitional cell carcinoma of the bladder and in a group of controls hospitalised with other diseases. As an indirect estimate of activating reactions (phase I) we measured cortisol hydroxylation, expressed as the ratio between urinary 6-beta-OH-cortisol and 17-OH-corticosteroids. Cortisol hydroxylation was not increased in the group of patients when compared with controls. The variations of phase II conjugating enzymes were followed indirectly by administering paracetamol and measuring the urinary excretion of its main metabolites over a period of 12 h. The variations in the metabolic conjugation of paracetamol were expressed as a percentage of each metabolite, or of unmodified paracetamol excreted in the urine, or as the ratio between a given metabolite and unmodified paracetamol. The data were analyzed with a logistic regression model, analysing the effects of possible confounding variables such as age, smoking, alcohol, blood nitrogen, blood creatinine, glutamic-pyruvic (SGPT), glutamic-oxalacetic transaminases (SGOT) and percent recovery of paracetamol in the urine. Statistical analysis showed that the excretion of mercapturate derivatives of paracetamol was significantly increased in the group of patients. The levels of glucuronic, sulphate and cysteine metabolites were not varied significantly. Since mercapturate derivatives are formed as a consequence of the formation of short-lived metabolites of paracetamol which react with protein, nucleic acids or glutathione, the increased excretion of mercapturic acid derivatives in cancer patients might be an indication of a higher capability of forming reactive molecular species from xenobiotic compounds. We suggest that this factor might play a role in the induction of bladder cancer.

The epidemiology of bladder cancer: a second look

A case-control study among 574 male and 158 female bladder cancer patients and equal numbers of matched controls was conducted between 1969 and 1974 in 17 hospitals in six United States cities. We determined that cigarette smokers of both sexes were at higher relative risk than nonsmokers. Cigarette smoking was responsible for about one-half of male and one-third of female bladder cancer. There was an excess of bladder cancer patients with some previous occupational exposure, such as rubber, chemicals, and textiles. A weak association with coffee drinking, which appeared to be independent of smoking, was found for males. Users of artificial sweeteners were not over-represented among the cases. The authors conclude that the epidemiologic pattern of bladder cancer cannot be fully accounted for by cigarette smoking and occupational exposure and suggest a series of metabolic studies to assess the role of additional factors, such as nutrition.

The prophylaxis of nonindustrial urothelial tumours

Present knowledge concerning carcinogenesis and the natural history of urothelial tumours precludes firm conclusions relative to nonindustrial prophylaxis. However, a number of measures are consistent with current data and may be instituted for those patients with a demonstrated propensity to urothelial tumours. Their acceptability is based on the lack of associated toxicity for the patient. These measures include the elimination of significant infection, cigarettes, artificial sweeteners, analgesic abuse and coffee, the administration of vitamins C and B(6), and in selected cases, the use of thiotepa. It is emphasized that the merit of these steps in altering the natural history of urothelial tumours is uncertain.

Bladder tumours and smoking

The smoking habits of 381 male bladder tumour patients, 412 lung cancer patients and 275 surgical controls were compared. The association between current cigarette smoking and lung cancer was demonstrated but no clear association was shown between smoking and bladder cancer. The data are compatible with a weak relationship with substantial current cigarette smoking only, as in other studies, but could also be consistent with a stronger association masked by some other carcinogenic hazard. The data strongly suggest that the prognosis of the original bladder tumour or of recurrences was worse in those who continued to smoke than in non‐ and ex‐smokers.